4-layer structure reflection type photocathode and photomultiplier using the same

Abstract

A high performance reflection type photocathode for use in a photomultiplier tube is formed by sequentially depositing three layers on a substrate made of nickel. The first layer is made of either one of chromium, manganese and magnesium as a major component and is deposited over the substrate. The second layer is made of aluminum as a major component and is deposited over the first layer. The third layer is made of antimony and at least one kind of alkaline metals and is deposited over the second layer.

What is claimed is: 
     
       1. A reflection type photocathode for use in a photomultiplier tube, comprising: a substrate   a first layer containing chromium as a major component and being deposited over said substrate;   a second layer containing aluminum as a major component and being deposited over said first layer; and   a third layer containing antimony and at least one kind of alkaline metal and being deposited over said second layer.   
     
     
       2. The photocathode according to claim 1, wherein said first layer has a thickness in a range of from 20 to 500 angstrom. 
     
     
       3. The photocathode according to claim 1, wherein said third layer has a thickness obtained by depositing 5 to 15 μg/cm 2  of a material containing said antimony and said at least one kind of alkaline metal over said second layer. 
     
     
       4. A reflection type photocathode for use in a photomultiplier tube, comprising: a substrate;   a first layer containing manganese as a major component and being deposited over said substrate;   a second layer containing aluminum as a major component and being deposited over said first layer; and   a third layer containing antimony and at least one kind of alkaline metal and being deposited over said second layer.   
     
     
       5. The photocathode according to claim 4, wherein said first layer has a thickness in a range of from 20 to 500 angstrom. 
     
     
       6. The photocathode according to claim 4, wherein said third layer has a thickness obtained by depositing 5 to 15 μg/cm 2  of a material containing said antimony and said at least one kind of alkaline metal over said second layer. 
     
     
       7. A reflection type photocathode for use in a photomultiplier tube, comprising: a substrate;   a first layer containing magnesium as a major component and being deposited over said substrate;   a second layer containing aluminum as a major component and being deposited over said first layer; and   a third layer containing antimony and at least one kind of alkaline metal and being deposited over said second layer.   
     
     
       8. The photocathode according to claim 7, wherein said first layer has a thickness in a range of from 20 to 500 angstrom. 
     
     
       9. The photocathode according to claim 7, wherein said third layer has a thickness obtained by depositing 5 to 15 μg/cm 2  of material containing said antimony and said at least one kind of alkaline metal over said second layer. 
     
     
       10. A photomultiplier comprising: a glass envelope;   a photocathode disposed within said glass envelope, said photocathode comprising a substrate, a first layer containing one selected from the group consisting of chromium, manganese and magnesium as a major component and being deposited over said substrate, a second layer containing aluminum as a major component and being deposited over said first layer, and a third layer containing antimony and at least one kind of alkaline metal and being deposited over said second layer;   at least one dynode disposed within said glass envelope to receive photoelectrons produced from said photocathode; and   anode disposed within said glass envelope to correct secondary electrons emitted from said dynode, a signal current being derived from said anode.   
     
     
       11. The photomultiplier according to claim 10, wherein said first layer of said photocathode has a thickness in a range of from 20 to 500 angstrom. 
     
     
       12. The photocathode according to claim 10, wherein said third layer of said photocathode has a thickness obtained by depositing 5 to 15 μg/cm 2  of material containing said antimony and said at least one kind of alkaline metal over said second layer.